32 research outputs found
CNN-based Prediction of Network Robustness With Missing Edges
Connectivity and controllability of a complex network are two important
issues that guarantee a networked system to function. Robustness of
connectivity and controllability guarantees the system to function properly and
stably under various malicious attacks. Evaluating network robustness using
attack simulations is time consuming, while the convolutional neural network
(CNN)-based prediction approach provides a cost-efficient method to approximate
the network robustness. In this paper, we investigate the performance of
CNN-based approaches for connectivity and controllability robustness
prediction, when partial network information is missing, namely the adjacency
matrix is incomplete. Extensive experimental studies are carried out. A
threshold is explored that if a total amount of more than 7.29\% information is
lost, the performance of CNN-based prediction will be significantly degenerated
for all cases in the experiments. Two scenarios of missing edge representations
are compared, 1) a missing edge is marked `no edge' in the input for
prediction, and 2) a missing edge is denoted using a special marker of
`unknown'. Experimental results reveal that the first representation is
misleading to the CNN-based predictors.Comment: In Proceedings of the IEEE 2022 International Joint Conference on
Neural Networks (IJCNN
Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass
We present a state-of-the-art calculation of the isovector quark helicity
Bjorken- distribution in the proton using lattice-QCD ensembles at the
physical pion mass. We compute quasi-distributions at proton momenta ~GeV on the lattice, and match them systematically to the
physical parton distribution using large-momentum effective theory (LaMET). We
reach an unprecedented precision through high statistics in simulations,
large-momentum proton matrix elements, and control of excited-state
contamination. The resulting distribution with combined statistical and
systematic errors is in agreement with the latest phenomenological analysis of
the spin-dependent experimental data; in particular, .Comment: 6 pages, 4 figure
Strong magnon-magnon coupling in an ultralow damping all-magnetic-insulator heterostructure
Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount
importance for spin-wave or magnonic devices as their ultralow damping enables
ultralow power dissipation that is free of Joule heating, exotic magnon quantum
state, and coherent coupling to other wave excitations. Magnetic insulator
heterostructures bestow superior structural and magnetic properties and house
immense design space thanks to the strong and engineerable exchange interaction
between individual layers. To fully unleash their potential, realizing low
damping and strong exchange coupling simultaneously is critical, which often
requires high quality interface. Here, we show that such a demand is realized
in an all-insulator thulium iron garnet (TmIG)/YIG bilayer system. The ultralow
dissipation rates in both YIG and TmIG, along with their significant spin-spin
interaction at the interface, enable strong and coherent magnon-magnon coupling
with a benchmarking cooperativity value larger than the conventional
ferromagnetic metal-based heterostructures. The coupling strength can be tuned
by varying the magnetic insulator layer thickness and magnon modes, which is
consistent with analytical calculations and micromagnetic simulations. Our
results demonstrate TmIG/YIG as a novel platform for investigating hybrid
magnonic phenomena and open opportunities in magnon devices comprising
all-insulator heterostructures.Comment: 45 pages, 18 figures, and 2 table
Experimental evidence for Berry curvature multipoles in antiferromagnets
Berry curvature multipoles appearing in topological quantum materials have
recently attracted much attention. Their presence can manifest in novel
phenomena, such as nonlinear anomalous Hall effects (NLAHE). The notion of
Berry curvature multipoles extends our understanding of Berry curvature effects
on the material properties. Hence, research on this subject is of fundamental
importance and may also enable future applications in energy harvesting and
high-frequency technology. It was shown that a Berry curvature dipole can give
rise to a 2nd order NLAHE in materials of low crystalline symmetry. Here, we
demonstrate a fundamentally new mechanism for Berry curvature multipoles in
antiferromagnets that are supported by the underlying magnetic symmetries.
Carrying out electric transport measurements on the kagome antiferromagnet
FeSn, we observe a 3rd order NLAHE, which appears as a transverse voltage
response at the 3rd harmonic frequency when a longitudinal a.c. current drive
is applied. Interestingly, this NLAHE is strongest at and above room
temperature. We combine these measurements with a scaling law analysis, a
symmetry analysis, model calculations, first-principle calculations, and
magnetic Monte-Carlo simulations to show that the observed NLAHE is induced by
a Berry curvature quadrupole appearing in the spin-canted state of FeSn. At a
practical level, our study establishes NLAHE as a sensitive probe of
antiferromagnetic phase transitions in other materials, such as moir\'e
superlattices, two-dimensional van der Waal magnets, and quantum spin liquid
candidates, that remain poorly understood to date. More broadly, Berry
curvature multipole effects are predicted to exist for 90 magnetic point
groups. Hence, our work opens a new research area to study a variety of
topological magnetic materials through nonlinear measurement protocols
Field Emission of Multi-Walled Carbon Nanotubes from Pt-Assisted Chemical Vapor Deposition
Multi-walled carbon nanotubes (MWNTs) were grown directly on a metal substrate with the assistance of Pt using a chemical vapor deposition method. In addition, the growth mechanism of Pt-assisted catalytic CNT was discussed. MWNTs were characterized by SEM, TEM, AFM, Raman, and EDS, and the field emission (FE) properties were investigated, comparing with the direct grown MWNTs. The results showed that CNTs could not been synthesized by Pt particles alone under the experimental condition, but Pt may accelerate the decomposition of the carbon source gas, i.e., assisting MWNT growth with other catalysts. The Pt-assisted MWNTs were longer with larger diameters of around 80 nm and possessed better structural qualities with very few catalyst particles inside. Improved field emission properties were demonstrated for the Pt-assisted MWNTs with lower turn-on fields (for 0.01 mA·cm−2 current density) of 2.0 V·μm−1 and threshold field (for 10 mA·cm−2 current density) of 3.5 V·μm−1, as well as better stability under a long-term test of 80 h (started at 3.0 mA for the Pt-assisted emitter and 3.25 mA for the direct grown emitter). This work demonstrated a promising approach to develop high performance CNT field emitters for device applications
Generating Giant Membrane Vesicles from Live Cells with Preserved Cellular Properties
Biomimetic giant membrane vesicles, with size and lipid compositions comparable to cells, have been recognized as an attractive experimental alternative to living systems. Due to the similarity of their membrane structure to that of body cells, cell-derived giant plasma membrane vesicles have been used as a membrane model for studying lipid/protein behavior of plasma membranes. However, further application of biomimetic giant membrane vesicles has been hampered by the side-effects of chemical vesiculants and the utilization of osmotic buffer. We herein develop a facile strategy to derive giant membrane vesicles (GMVs) from mammalian cells in biofriendly medium with high yields. These GMVs preserve membrane properties and adaptability for surface modification and encapsulation of exogenous molecules, which would facilitate their potential biological applications. Moreover, by loading GMVs with therapeutic drugs, GMVs could be employed for drug transport to tumor cells, which represents another step forward in the biomedical application of giant membrane vesicles. This study highlights biocompatible GMVs with biomimicking membrane surface properties and adaptability as an ideal platform for drug delivery strategies with potential clinical applications